Cardiac assist devices have been known and used for many years for assisting the contractions of a weak or diseased heart. For example, the Anstadt cup employs an outer glass housing with an inner diaphragm which is held onto the cardiac ventricles by suction. Alternating positive and negative pressures are delivered into the space between the cup and diaphragm to effect systolic contraction and diastolic relaxation. However, the suction required to hold the Anstadt cup in place can cause damage to the heart muscle.
U.S. Pat. No. 4,690,134 issued to Snyders also discloses an external ventricular assist device which utilizes inflatable chambers within a shell for supplementing cardiac output. The Snyders device is sutured to the pericardial sac. Thus, the Snyders device is not intended for short term use, such as to provide cardiac assist during surgery.
Internal cardiac assist devices are also known, but generally require the use of an anticoagulant to thin the blood, which leads to increased bleeding. Arterial balloon pumps also require an anticoagulant.
Therefore, a primary objective of the present invention is the provision of an improved external cardiac assist device.
Another objective of the present invention is the provision of a cardiac assist device which is useful for short term and long term applications.
A further objective of the present invention is the provision of a cardiac assist device which can be used during sudden decompensation of the heart, shortly after heart surgery to support low cardiac output, as a bridge to transplantation, and to permanently augment the heart.
Still another objective of the present invention is the provision of a cardiac assist device which eliminates the need for an anticoagulant, which eliminates neurological injury secondary to potential emboli, which eliminates the need for multiple cannulation techniques, and which reduces bleeding complications.
Still another objective of the present invention is the provision of a cardiac assist device which prevents cardiac rhythmic problems or fibrillation.
A further objective of the present invention is the provision of a cardiac assist device which utilizes chambers which can be adjustably inflated to provide varying degrees of cardiac assist and for various sized hearts.
An additional objective of the present invention is the provision of a cardiac assist device which can be fixed to the heart without the use of suction or sutures.
Another objective of the present invention is the provision of an external cardiac assist device which can be quickly and easily employed.
Another objective of the present invention is the provision of a cardiac assist device which is safe in use and medically acceptable.
These and other objectives will become apparent from the following description of the invention.